Just a little research puts the lie to this attractive and commonly held misconception.

Along with fossil carbon that becomes carbon dioxide in combustion, fossil fuels bring up fossil hydrogen that becomes water in combustion. High-efficiency combustion that recovers all the excess heat can recover this as condensed fresh water, adding to local supplies.

Fracking is transitioning from a paradigm of bringing water to the drilling site, to one of using water already present at the site in deep saline aquifers. There is so much surplus energy in the first 30 days of production when the equipment is still on site, that it is proving more economical to use some of that energy to clean the extracted hydrocracking fluid and purify the water to conditions acceptable for release at the surface, rather than to pay for it to be hauled away and treated as waste. So fracking is becoming a source of freshwater as well. Fossil fuel drilling becoming a local fresh water source instead of a sink is a very real and transformational trend.

The water footprint of natural gas to electricity is about 0.11 M3/GJ, for solar thermal it is about 0.27 M3/GJ, and for biomass it is about 70 M3/GJ (Mekonnen 2010). Biofuels consume 50 to 5,000 times more water per unit of energy delivered than fossil fuels. The most water-efficient biofuel path to date is sugar beet with a water footprint of 790 liters of water per liter of ethanol produced. The worst is jatropha biodiesel with a footprint of nearly 20,000 liters per liter. Refined gasoline from crude oil has a footprint of about 6 liters per liter. Biofuels are the worst idea ever for a world where a growing fraction of the population is already water poor and where land is being “green grabbed” for offshore food and industrial agriculture in the poorest countries of the world by the richest countries.

The favorable numbers for water usually claimed for wind and solar only consider the operational phase of their lifecycle and ignore the energy and water-intensive mining and manufacturing and transporting and erecting and decommissioning phases of their lifecyle which are very high compared to alternatives when normalized to units of energy delivered over their hardware lifetime.

Most of the favorable assumptions behind the push for “clean and green” energy do not survive scrutiny. We need to take the measurements and do the math to make sound decisions in the 21st century.